Devices for measuring the light absorbing, reflecting, fluorescing, and other optical characteristics of substances such as tissue cells in suspension or cultured on a coverslip, are often used to measure the presence and concentration of particular substances, which can be helpful such as in various biomedical and physiological contexts. For example, a cuvette-based fluorometer system has been used to measure the presence and concentration of substances (e.g., Ca.sup.2+) in biological cells such as cardiac cells, wherein the cells are cultured on a coverslip fixed into a predetermined position within the cuvette.
In the past, however, such coverslips have been mounted at an angle to incoming excitation light, and fluorescence or other optical characteristics induced by the excitation light is received by a monitor device (such as an emission monochromator) situated at an angle of approximately 90 degrees to the incoming excitation light path. Generally this angled orientation between the incident excitation light and the emitted fluorescence or other optical phenomenon was utilized to minimize contamination of monitored emissions by the incoming excitation light. Once the coverslip is fixed in a diagonal manner, the volume of solution in the cuvette is often perfused, such as through inlet and outlet tubes and a peristaltic pump.
An example of the predetermined angular arrangement of excitation light relative to the monitored emissions is shown in U.S. Pat. No. 4,008,397, which issued to J. Zdrodowski. In this patent, a fluorimeter flow cell is described as being constructed entirely of clear plastic tubing, as opposed to utilizing the more traditional quartz flow cells. The plastic tubing is essentially transparent to ultra-violet light at a predetermined wavelength which is passed through an inlet aperture to impinge upon the material in the tube. If fluorescent material is present in the tube, the fluorescent radiation will be emitted from the tubing through an outlet aperture oriented at 90 degrees to the entry aperture.
Another fluorimeter utilizing a flow cell is shown in U.S. Pat. No. 4,531,834 which issued to T. Nogami. Again in the Nogami flow cell, fluorescent light is emitted at a 90 degree angle to the incident light for reception by a photocell. A processor compares and utilizes the detected transmission light and the intensity of the fluorescent light to automatically compensate for variation of intensity of the light source.
U.S. Pat. No. 4,989,974 which issued to K. Anton et al., describes the diverse use of flow cells for liquid chromatography (LC), supercritical fluid chromatography (SFC), gas chromatography (GC) and capillary zone electrophoresis (CZE) in order to provide measurements and analysis of predefined volumes of sample solutions in a known environment. Anton et al. describe the fact that gaps between the flow cell and the detector can often lead to increased background noise and drift phenomenon during measurement procedures. The micro-flow cell described by Anton et al. provides two diametrically opposite light permeable passages on a holding device comprising two substantially identical shell halves. Incident light is permitted to pass through one of the light permeable passages, while a photoconductor is attached to an adjacent passage. The adjacent passages are located at 90 degree angles to one another, whereby measured luminescence or the like is again received at a 90 degree angle to the incident light.
Consequently, while the use of flow cell devices is widespread and well known in the industry for use in conjunction with a sample vessel such as a cuvette and devices for measuring light absorbing, fluorescence, and reflecting characteristics of cell material; heretofore, there has not been provided a coverslide device satisfactory for front face testing procedures. Moreover, prior art arrangements tended to allow for inexact gaps between the coverslips or other sample cell arrangements and the emission detector devices utilized to monitor optical phenomenon. As the prior art specifically suggests, such variations often allow for unacceptable levels of interference and imprecision, and reduce the sensitivity and adaptability of the testing setup.